The problem with headphone FR is we are in the waves lengths in medium/treble between the tranducer and the mike. So, with the stationnary waves, a flat curve will surely not be linear to our ears. I believe our ears will not produce the same resonances.
Looking at various headphones on this site we can see different devices had near the same resonances. I believe it depend more or less from the distance between the transducer and the mike too, because there is no reason different membranes resonates the same ?Learning Center - Build a Headphone Graph | HeadRoom Audio
We can makes us an idea of an average ideal response curve witch will sound flat to our ears/brains ? Then we should apply an invert of this curve to correct our measurements, in order to can read a flat curve for a neutral headphone.?

Richard,
The automatic equalization of these headphones for frequency response will be a great thing as long as the price is low enough. What this doesn't do anything about is the actual sound of the membrane used in the headphone and the decay rate of the diaphragm. Just correcting the frequency response alone will not a great headphone make. The difference between a Mylar diaphragm and perhaps a metallic diaphragm or anything else would have to be looked at. I would be just as interested in the waterfall plots of decay time for these headphones as I would the simple frequency response curves. Anyone else have anything to say about the sound of any of these headphones after eq correction?

We all know this, dont we? You need to get the freq response right FIRST and foremost. Then the others --- a matter of priorities. The deviations are huge! get it taken care of and then focus on the rest. Like I said... pick the ones with the lowest distortion to do an auto-EQ with and you will be amazed. I use 3 headphones to play with -- the HiFiman HE500; The Sennheiser HD800, the AKG 702 and a Panasonic and an electrostatic. I have done what i showed and it makes a big difference and improvement - both. Do it and THEN move on to fixing all the other secondary issues. Trust me on this. It works and can be cheaply done in dsp chip.

If you want to experiment with auto EQ, buy a used reciever and use the auto-EQ that is built-in as described via headphone jack. Maybe even a DIY of taking out that auto-EQ and put it in a seperate box with upscale opamps et al.

I can see a headphone company doing this sort of thing or a high-end small company getting it going.

The problem with headphone FR is we are in the waves lengths in medium/treble between the tranducer and the mike. So, with the stationnary waves, a flat curve will surely not be linear to our ears. I believe our ears will not produce the same resonances.
Looking at various headphones on this site we can see different devices had near the same resonances. I believe it depend more or less from the distance between the transducer and the mike too, because there is no reason different membranes resonates the same ?Learning Center - Build a Headphone Graph | HeadRoom Audio
We can makes us an idea of an average ideal response curve witch will sound flat to our ears/brains ? Then we should apply an invert of this curve to correct our measurements, in order to can read a flat curve for a neutral headphone.?

This type of work has been explored extensively over the decades and artifitial ears produced that mimic very closely the ear. Its been thoroughly developed. My 'before' is very close to the results done via dummy head/ears when compared. i believe mine results are more accurate as it used a real ear and can be as accurate with each individual persons ear size/shhape/volume.

This has all been considered and done before this moment in time. i am giving you the short story version... something all can try for them selves. BTW - this is covered in Linear Audio mag along with my headphone amp saga.

Note: the headphone companies try to eq their models to have particular curves... some free field compensated and the like. The Sennheiser is Flat based upon certain principles within a narrow dB tolerance. Others may not be. Try it with your headphones and see if the sound isnt better flat at your ear's entrance.

My 'before' is very close to the results done via dummy head/ears when compared. i believe mine is more accurate as it used a real ear and can be as accurate with each individual persons ear.

Can-you describe this 'dummy head+ears' ? Molding of a real ear in silicon ? Then record of a flat loudspeaker in open ear to calibrate ?
(Excuse-me, Richard, i have no experience in headphone design, neither had read a lot about.)

The problem with headphone FR is we are in the waves lengths in medium/treble between the tranducer and the mike. So, with the stationnary waves, a flat curve will surely not be linear to our ears. I believe our ears will not produce the same resonances.
Looking at various headphones on this site we can see different devices had near the same resonances. I believe it depend more or less from the distance between the transducer and the mike too, because there is no reason different membranes resonates the same ?Learning Center - Build a Headphone Graph | HeadRoom Audio
We can makes us an idea of an average ideal response curve witch will sound flat to our ears/brains ? Then we should apply an invert of this curve to correct our measurements, in order to can read a flat curve for a neutral headphone.?

Your questions are good but too lengthy for reply here. See Sennheiser's web site about the calibration of each of thier HD800. See how they do it.

You can also look up dummy heads for headphone testing. The makers have extensive R&D on it.
Demian Martin has one for headphone testing and has tested a number of headphones with it.
-RNM

Thank you Richard,
The last nice set of headphones I remember hearing were electrostatic headphones from Sennheiser if I remember correctly. I'll have to get a copy of the Linear Audio article and read what you have done and created. It is an interesting field as it is so much different working with the closed air chamber of a headphone compared to a typical loudspeaker. I would never expect to achieve the same audio conditions of only hearing through the ears and not the entire body sensations and left right ear discrimination as with speakers but there are times when you don't want to disturb everyone else, so headphones definitely have their place in our systems.

The problem with headphone FR is we are in the waves lengths in medium/treble between the tranducer and the mike.

The pressure in the small volume is equal everywhere. The distance between ear canal opening and the diaphram is a fraction of an inch... any such affects are at very highest freq only. Sometimes above the BW of the drivers. I moved the probe all around inside the area and didnt get different response curves. That was the very first issue I wanted to know also. If it varied then averaging would be needed like in rooms. it isnt there with the short distance and volume we have with headphones.

Thank you Richard,
I would never expect to achieve the same audio conditions of only hearing through the ears and not the entire body sensations.

This is a real condition which causes problems when recording... using headphones vs using speakers to monitor with.

The physical sensation when missing causes you to add EQ in the bass to compensate.... so it resembles speaker sound. Then when played over speakers, it sounds like too much bass. And, visa versa... Monitored with speakers leaves one feeling a loss of bass when listening with headphones. this is the basis of why some headphones have bass boost... some switchable.. on-off. Most recordings are recorded/eq'ed over speakers and when headphones are used to listen to them, they need some bass boost to 'sound' flat. Well know issue in recording field and one I learned and experimented with when i did live Bay Area recordings back in the day.

Thank, Richard. I confirm i was never able to mix or equalize basses instruments with headphones. But it is helpfull to fine tune effects, reverberations, stereo image and room size, and verify little details you cannot always hear with monitors. Too, sometimes, it is difficult to separate some instruments in the monitors, and headphones help to listen to them more precisely.
About bass boost, i like The Porta Pro for that, while my Sennheizer (HD230, HD430) have too much of unnatural trebles. The 230 dual transducer is VERY disagreeable.
My AKG is a K240, with bass resonators, witch are just adding a lot of resonances and blurr.